CN114567525A

CN114567525A - Channel estimation method and device

Info

Publication number: CN114567525A
Application number: CN202210045007.XA
Authority: CN
Inventors: 刘丹谱; 田永清; 张志龙; 尹长川
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2022-01-14
Filing date: 2022-01-14
Publication date: 2022-05-31
Anticipated expiration: 2042-01-14
Also published as: CN114567525B

Abstract

The invention provides a channel estimation method and a device, wherein the method comprises the following steps: constructing a measurement matrix according to the beam pair scanning result; and predicting an optimal high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology. The invention provides a large-scale MIMO channel estimation method based on 5G/B5G, which is based on beam pair scanning and compressive sensing technology.A base station and a user terminal traverse all communication beam pairs through a synchronous signal block at the initial stage of beam pair scanning, measure the signal intensity of all the beam pairs and sequence the beam pairs from large to small to construct a measurement matrix; on the basis, the high-dimensional original channel estimation problem is converted into sparse channel estimation of an angle domain, channel information is recovered by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode, and accurate estimation of a channel can be realized with low algorithm complexity.

Description

Channel estimation method and device

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a channel estimation method and apparatus.

Background

Millimeter wave (mmWave) communication, which is a key technology of Fifth Generation mobile communication/super Fifth Generation mobile communication (five Generation/Beyond five Generation, 5G/B5G) systems, has a larger bandwidth, a lower latency, and a higher transmission rate. In order to overcome the high path loss of millimeter waves, a large-scale Multiple-Input Multiple-Output (MIMO) technology and a beam forming technology are widely applied to gather data information in a single beam direction for transmission, so as to increase the coverage of communication. Channel State Information (CSI) plays a very critical role in the millimeter wave communication process, and the receiving end can perform signal detection by using the CSI obtained by Channel estimation, and can determine the optimal beam direction of the transmitting and receiving end based on the CSI in a mobile environment, thereby improving the transmission performance.

Whereas the communication frequency of B5G has been increased above 52.6GHz, to combat the more severe communication path loss, both base stations and user terminals need to be equipped with larger-scale phased array antennas whose antenna radiating elements vary from tens to hundreds, which results in a significant increase in channel dimensions.

Traditional channel estimation algorithms such as LS, LMMSE, DFT and the like involve a large number of operations with high computation complexity such as matrix multiplication, inversion and the like, which brings great challenges to base stations and terminals with limited computing power.

In summary, in the scenario of discrete-grid (Off-grid) channel communication with high frequency and large bandwidth, how to design a low-complexity channel estimation algorithm to acquire CSI is one of the problems that needs to be solved in future communication.

Disclosure of Invention

The invention provides a channel estimation method and a device, which are used for solving the defect of high calculation complexity in the channel estimation process in the prior art, are suitable for communication between a base station and a single user terminal and can be easily expanded to a multi-user terminal scene.

In a first aspect, the present invention provides a channel estimation method, including:

constructing a measurement matrix according to the beam pair scanning result;

and predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology.

According to the signal channel estimation method provided by the invention, the construction of the measurement matrix according to the beam pair scanning result comprises the following steps:

step 1, traversing all possible beam pair combinations for communication between a base station and a user terminal through beam pair scanning, and determining the received signal strength of pilot signals in each group of beam pairs in the beam pair combinations;

and 2, combining and constructing an initial arrival and departure angle set by the beam pairs with the received signal strength greater than the first threshold value, and determining a measurement matrix on each subcarrier.

According to the signal channel estimation method provided by the invention, the high-dimensional original channel between the base station and the user terminal is predicted by utilizing the measurement matrix based on the adaptive compressed sensing technology, and the method comprises the following steps:

step 3, calculating a correlation value between the initial measurement matrix and the observation value on the corresponding pilot frequency to obtain an arrival angle and a departure angle corresponding to the maximum correlation value;

step 4, taking the arrival and departure angles as centers, quantizing the surrounding local angle space to obtain a local measurement matrix corresponding to the surrounding local angle space;

step 5, recalculating the correlation value between the local measurement matrix and the observed value on the corresponding pilot frequency to determine a new arrival and departure angle corresponding to the obtained maximum correlation value;

step 6, determining an angle offset according to the new arrival and departure angle and the arrival and departure angle;

step 7, introducing the angle offset into the initial arrival and departure angle set, and updating the initial measurement matrix;

step 8, iteratively executing the steps 3 to 7 until the difference between the correlation values calculated in the two adjacent iterative processes is smaller than a second threshold value, and acquiring target arrival and departure angles to determine target paths corresponding to the target arrival and departure angles;

and step 9: removing the beam pairs corresponding to the target path from all possible beam pair combinations, recombining the beam pair combinations by the remaining beam pairs, and determining the received signal strength of pilot signals in each group of beam pairs in the beam pair combinations;

step 10: iteratively executing the steps 2 to 9 until all target paths corresponding to the beam pair combination, target arrival and departure angles corresponding to all the target paths and an antenna array response set are obtained;

step 11: and calculating the complex gain and the original channel corresponding to each target path according to the target arrival and departure angle and the antenna array response set corresponding to each target path so as to construct the high-dimensional original channel.

According to a signal channel estimation method provided by the present invention, traversing all possible beam pair combinations for communication between a base station and a user terminal through beam pair scanning, and determining received signal strength of pilot signals in each group of beam pairs in the beam pair combinations, includes:

in the initial access stage of the user terminal, after a baseband pilot frequency at the base station side sends an initial signal and is coded by a simulation precoding vector, the coded pilot frequency signal is sent to the user terminal in a beam pair mode;

and the user terminal traverses all the beam pairs between the user terminal and the base station so as to decode the pilot signals in each group of received beam pairs by using the analog pre-decoding vector and calculate the received signal strength of the pilot signals in each group of beam pairs.

According to a signal channel estimation method provided by the present invention, the combining and constructing an initial arrival and departure angle set from the beam pairs whose received signal strength is greater than a first threshold value, and determining a measurement matrix on each subcarrier includes:

according to the intensity of the received signal, the received signal is strengthenedAll the wave beam pairs with the degrees larger than the first threshold value are sequenced, an initial arrival and departure angle set is constructed, and the top N is obtained_RFSimulating a pre-coding vector and a simulating pre-decoding vector corresponding to the group wave beam;

according to the arrival and departure angle set, N_RFAnd constructing a measurement matrix for each subcarrier of the channel on the frequency domain for the analog pre-coding vector, the analog pre-decoding vector and the pilot frequency sequence.

According to a signal channel estimation method provided by the present invention, the calculating a correlation value between the initial measurement matrix and an observed value on a corresponding pilot to obtain an arrival and departure angle corresponding to a maximum correlation value includes:

and sequentially calculating and summing correlation values of the initial measurement matrix on each subcarrier and the observation value on the corresponding pilot frequency, wherein the correlation values are used as the correlation values between each column of the initial measurement matrix and the observation value on the corresponding pilot frequency, and determining a column corresponding to the maximum correlation value from the correlation values to obtain the arrival and departure angles corresponding to the maximum correlation value.

According to the signal channel estimation method provided by the present invention, the method for quantizing the surrounding local angle space by taking the arrival and departure angles as the center to obtain the local measurement matrix corresponding to the surrounding local angle space comprises:

iteratively updating the arrival and departure angles in the surrounding local angle space by taking the arrival and departure angles as centers, acquiring each updated arrival and departure angle until iteration converges, and outputting local arrival and departure angles;

reconstructing a local measurement matrix for each subcarrier of the channel in the frequency domain based on the local arrival and departure angles.

In a second aspect, the present invention further provides a channel estimation apparatus, including:

the signal acquisition unit is used for constructing a measurement matrix according to the beam pair scanning result;

and the signal analysis unit is used for predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology.

In a third aspect, the present invention provides an electronic device, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the steps of the channel estimation method according to any of the above aspects.

In a fourth aspect, the present invention also provides a non-transitory computer-readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the channel estimation method as described in any of the above.

The invention provides a channel estimation method and a device, which are based on a 5G/B5G large-scale MIMO communication system and provide a large-scale MIMO channel estimation method based on beam pair scanning and compressed sensing technology.A base station and a user terminal traverse all communication beam pairs through a synchronous signal block at the initial stage of beam pair scanning, measure the signal intensity of all the beam pairs and sort the beam pairs from large to small to construct a measurement matrix; on the basis, the high-dimensional original channel estimation problem is converted into sparse channel estimation of an angle domain, channel information is recovered by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode, and accurate estimation of a channel can be realized with low algorithm complexity.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

Fig. 1 is a flow chart of a channel estimation method provided by the present invention;

fig. 2 is a schematic diagram of a structural model of a MIMO communication system provided by the present invention;

FIG. 3 is a second flowchart of the channel estimation method according to the present invention;

FIG. 4 is a schematic diagram of a structure of a synchronization signal block in a 5GNR provided by the present invention in a time-frequency domain;

FIG. 5 is a graph of simulation results of normalized mean square error of channel estimates under different algorithm comparisons;

FIG. 6 is a graph of simulation results of block error rates under different algorithm comparisons;

FIG. 7 is a diagram of simulation results of the normalized mean square error of channel estimation for the algorithm provided by the present invention under different antenna configurations;

FIG. 8 is a graph of simulation results of block error rates for the algorithm provided by the present invention under different antenna configurations;

FIG. 9 is a diagram of simulation results of normalized mean square error of channel estimation for an algorithm provided by the present invention for different initial AoA/AoD numbers provided by beam scanning;

FIG. 10 is a graph of simulation results of the block error rate for the algorithm provided by the present invention for beam scanning providing different initial AoA/AoD numbers;

fig. 11 is a schematic structural diagram of a channel estimation device provided in the present invention;

fig. 12 is a schematic structural diagram of an electronic device provided in the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that in the description of the embodiments of the present invention, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element. The terms "upper", "lower", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that embodiments of the application may be practiced in sequences other than those illustrated or described herein, and that the terms "first," "second," and the like are generally used herein in a generic sense and do not limit the number of terms, e.g., the first term can be one or more than one. In addition, "and/or" in the specification and claims means at least one of connected objects, a character "/" generally means that a preceding and succeeding related objects are in an "or" relationship.

Considering that the existing Channel estimation algorithm may involve a large number of operations with high complexity, such as matrix multiplication, inversion, etc., the Channel estimation method provided by the present invention, in order to obtain Channel State Information (CSI) using a Channel estimation algorithm with lower complexity, utilizes sparsity and low rank of the millimeter wave Channel in the Angle domain, i.e., the Channel Information is only related to a small number of angles of Arrival (AoA)/angles of departure (AoD), and is based on a Compressed Sensing (CS) technique to complete Channel estimation by measuring a matrix and a small number of parameters.

However, most of the current work today assumes that the AoA/AoD of a channel lies in a discretized angular grid, which is clearly unreasonable compared to random angles in real channels.

Further, the design of the existing channel estimation algorithm cannot be directly applied to a communication system with analog beamforming processing at the radio frequency front end, and the fundamental reason is that:

the dimension of the pilot signal at the baseband is limited by the number of radio frequency links (RF chains) and is much smaller than the number of radio frequency antennas at the transmitting and receiving ends, so that the beamforming vector needs to be combined to effectively obtain the complete CSI information.

In an actual communication system, beam directions are approximately kept unchanged in a short process of channel estimation, so that channel measurement can be actively performed in a plurality of different spatial directions in combination with a beam scanning mechanism in an initial access process, and by selecting those beam directions with higher received SIGNAL strength (RSRP) for transmission, an equivalent SIGNAL-to-NOISE RATIO (SNR) of a received SIGNAL is improved, thereby improving the accuracy of channel estimation.

On the other hand, the existing compressed sensing technology needs to quantize the complete angle space of the AoA/AoD and operate based on the complete quantized angle set, so that the calculation complexity of the algorithm is greatly increased.

In view of the above, the present invention provides a new channel estimation method and apparatus by improving the disadvantages existing in the existing channel estimation, and the channel estimation method and apparatus provided by the embodiments of the present invention are specifically described below with reference to fig. 1 to 12.

Fig. 1 is a schematic flow chart of a channel estimation method provided by the present invention, as shown in fig. 1, including but not limited to the following steps:

step 11: constructing a measurement matrix according to the scanning result of the beam pair;

step 12: and predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology.

It should be noted that the channel estimation method provided by the present invention mainly includes two major steps: and constructing a measurement matrix by using the beam scanning result, and finishing channel estimation by using an adaptive compressed sensing algorithm. The specific generation steps of other parameters are not limited, such as a beam scanning mechanism, baseband processing, digital precoding, analog precoding, etc., and the implementation of these related steps can be implemented by any existing scheme, which is not described in detail herein.

Fig. 2 is a schematic diagram of a structural model of an MIMO communication system provided by the present invention, and the channel estimation method provided by the present invention is applicable to the communication system shown in fig. 2, which is a downlink single-base-station single-user communication system with a radio frequency analog beamforming processing architecture at the front ends of both transceivers.

As shown in FIG. 2, data and pilot signals on the Base Station (BS) side are connected to N through baseband processing_BS,RFOn an RF link, and through a phase shifter and N_tConnecting the root antenna; the user terminal (UE) side deploys N in the same way_rRoot antennas connected to respective corresponding RF chains (N in total)_UE,RFLink), and finally obtains the original information through baseband processing.

The invention assumes that the base station supports transmission N when communicating with the user terminal_sA data stream, and satisfies: n is a radical of_t,N_r≥N_BS,RF,N_UE,RF≥N_s≥1。

Alternatively, the present invention contemplates a wideband geometric millimeter wave channel (ESV), whose time domain channel model may be expressed as follows:

wherein t represents the sampling time of the channel in the time domain; tau is_lIs the delay of the first path; δ (·) denotes an impulse response function; l represents the number of multipaths in the channel; h is_lIs N_r×N_t(ii) a Representing the MIMO channel response of the l path; alpha is alpha_lThe complex gain corresponding to the first path obeys complex Gaussian distribution with the mean value of 0 and the variance of 1; a is_r(θ_l) And a_t(φ_l) Respectively representing antenna array response vectors of a user terminal side and a base station side; theta_lAnd phi_lThe value ranges for the corresponding arrival angle AoA and departure angle AoD are [0,2 π]A random value of (a); λ represents a wavelength; d represents the spacing of the antenna elements and is typically taken to be half wavelength.

Because the time when different paths reach the receiving end is different, the channel will show the characteristic of frequency domain selective fading in the frequency domain, and according to the conversion relationship between the channel in the time domain and the frequency domain, the channel on the k-th subcarrier can be represented by the following matrix:

the number of time domain sampling points in each Orthogonal Frequency Division Multiplexing (OFDM) symbol is N, and is equal to the total number K of Frequency domain subcarriers in value; n is the nth sampling point in each OFDM symbol of the channel in the time domain; f. of_sIs the sampling frequency; h_kIs dimension N_r×N_tThe channel matrix of (2).

In the actual communication process, an initial signal s is transmitted at a base band pilot frequency at a transmitting end (BS side), and the dimension of the initial signal s is N_RF×N_sample，N_sampleThe number of samples in the time domain. s channelOver dimension of N_t×N_RFOf RF analog precoding vector F_RFAfter analog precoding, from N_tThe root antenna transmits in space to the receiving end (UE side) in the form of a beam pair.

The transmitted pilot signal x at the transmitting end can be represented as:

x＝F_RFs (6)

wherein the initial signal s satisfies | s ²1, i.e. the average power of the initial signal is 1.

On the other hand, at the receiving end (UE side), N_rThe pilot signal received by the root antenna has a pass dimension of N_r×N_RFIs simulated by predecoding vector W_RFAnd combining the data and obtaining the data sent by the sending end in the baseband. Since the channel includes a plurality of subcarriers in the frequency domain, the frequency domain received signal of the k-th subcarrier can be expressed as:

wherein eta is additive white Gaussian noise, obeys mean value of 0 and variance of sigma²Complex gaussian distribution of (a); f_RFAnd W_RFThe beamforming matrices, i.e. F, representing the transmitting and receiving ends, respectively_RFRepresenting the analog precoding vector, W, of the transmitting end_RFRepresenting the analog pre-decode vector at the receiving end,

is W_RFThe conjugate transpose of (1); s_kAnd y_kIndicating the signal of the baseband pilot s and the received signal y at the k-th subcarrier.

The invention uses the wave beam scanning mechanism in the initial access process of the UE side to ensure that the first N with the highest Signal Receiving Power (Reference Signal Receiving Power, RSRP) is used_RFAnalog precoding vector and analog predecoding vector generation F_RFAnd W_RF。

Note that, the analog precoding vector F is described above_RFAnd simulating the predecode vectorW_RFThe method can be realized by DFT codebook, BeamSteering codebook and other modes, and the invention can be realized by DFT codebook, that is, the weighting coefficient Q of the nth antenna in the mth code word in the codebook_m,nCan be expressed as:

wherein M is the number of codewords; p is the number of antennas; the codebook set is a set containing all code words, and each codebook corresponds to a group of beam pair directions, analog precoding vectors and analog predecoding vectors.

For the convenience of understanding, before describing the specific implementation steps of the present invention, the virtual channel representation of the millimeter wave MIMO channel in the angle domain and the power leakage problem caused by random AoA/AoD are introduced first.

Since the sparsity of the millimeter wave MIMO channel is apparent in the angular domain, most of the energy of the channel is concentrated on a few line-of-sight and line-of-sight (LOS/NLOS) paths.

To recover the high-dimensional original channel matrix H_kFirst, H is required to be_kConversion into virtual channel H with angle domain sparse characteristics_k,v(for simplicity, subscript k is omitted in subsequent examples), i.e.:

wherein H_v∈N_r×N_t，A_T∈N_t×N_t,A_R∈N_r×N_r；A_T,A_RIs an alternative beam forming matrix formed by DFT codebook, which respectively shows that AoD and AoA are in [0,2 pi ]]Angle of inner uniform quantization

Antenna array response set, and satisfies

I represents an identity matrix in which the number of quantization cells is N_t,N_rNamely:

the linear transformation in the above equation (9) is equivalent to uniformly quantizing a high-dimensional channel into N in the angular domain by using the beam vector combination between the BS and the UE_r×N_tLattice point, α_i,jI.e. the path gain corresponding to each angular field quantization grid point, where the time-varying effect is not considered, so that alpha at different times_i,jIs kept constant.

Virtual channel H_vCan clearly display the sparsity of a high-dimensional original channel matrix H, when the true AoA/AoD of a channel is just positioned in a quantization angle set, H_vThe number of non-zero elements is equal to the number L of channel paths, and L & lt N_r×N_t(ii) a The real channel AoA/AoD is randomly generated and cannot be completely located in the quantized angle set, and thus power leakage, i.e., H, appears in a combination of multiple quantized AoA/AoD angles_vThe number of non-zero values present in is greater than L. But both can reflect the sparsity of the channel in the angle domain, so H_vThe estimation is converted into a sparse reconstruction problem, and an original high-dimensional channel matrix H is recovered based on the following mapping relation:

further, to realize H_vIn the sparse reconstruction of (3), the expression of the received signal y can be obtained by substituting equation (7) with equation (11) in consideration of the communication system model with analog beamforming processing at the front end shown in fig. 2, and thus:

wherein vec (y) represents a vectorization operation on y;

representing a kronecker product operation; measuring matrix

Dimension of N_RFN_sample×N_rN_tI.e. each column corresponds to a set of quantisations

Vector sum representing incomplete sparse vector h for virtual channels_v＝vec(H_v) Dimension N_rN_tX 1; η' is white gaussian noise.

From the above analysis, it can be seen that the estimation of the high-dimensional original channel matrix H can be transformed into the estimation of the incomplete sparse vector H_vAnd (4) solving.

Theories prove that the compressed sensing technology can recover sparse vectors based on measurement matrixes and observed values which meet conditions, so that the construction of the measurement matrix phi is very important.

In the formula (13), the measurement matrix Φ includes the analog beamforming matrix F of both the transmitting and receiving sides_RF/W_RFAlternative beam space A_R,A_TIncluding all possible AoA/AoD combinations in space.

Considering the narrow beams in high-frequency millimeter wave communication, the number of available beam pairs is huge, but the sparsity of the channel causes the received signal energy in the direction of most of the beam pairs to be low. In the case of a small number of measurements required for compressed sensing, a situation occurs in which most of the measurements are in a low SNR state, thereby seriously affecting the estimation performance. At the same time, all AoA/AoD combinations also contribute to higher computational complexity of the channel estimation algorithm.

Therefore, in step 11, the present invention proposes to utilize the prior information obtained by beam scanning in the initial access process at the UE side to limit the candidate beam space, and select a beam pair combination with RSRP greater than the first threshold to form the candidate beam space and the measurement matrix Φ.

Further, in step 12, for the power leakage problem caused by the random angle of the channel, on the basis of beam scanning, the adaptive compressed sensing technology is used to track the angle of each path, so as to recover the original channel information in high dimension.

In the initial stage of beam pair scanning, a base station and a user terminal traverse all communication beam pairs through a synchronous signal block, measure the signal intensity of all the beam pairs and sequence the beam pairs from large to small to construct a measurement matrix; on the basis, the high-dimensional original channel estimation problem is converted into sparse channel estimation of an angle domain, channel information is recovered by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode, and accurate estimation of a channel can be realized with low algorithm complexity.

Fig. 3 is a second flowchart of the channel estimation method provided by the present invention, and as shown in fig. 3, the step 11 of constructing the measurement matrix according to the beam pair scanning result may include, but is not limited to, the following steps:

Specifically, the invention provides a MIMO channel estimation method based on beam scanning and compressive sensing technology, a receiver at a UE side can complete channel estimation according to received signals y on all subcarriers and beam scanning results in an initial access process, and the main steps are as follows:

step 1, the BS and the UE traverse all possible wave beam combinations of both communication parties through wave beam scanning to obtain the RSRP of pilot signals in each group of wave beam pairs in the direction.

And 2, selecting a beam pair with the RSRP larger than a first threshold value, and combining to construct an initial AoD/AoA set and a measurement matrix phi on each subcarrier.

As an alternative embodiment, the traversing all possible beam pair combinations for the base station to communicate with the user terminal through beam pair scanning, and determining the received signal strength of the pilot signal in each group of beam pair directions in the beam pair combinations includes:

Optionally, in step 1, in the initial access stage of the UE, the BS and the UE add beam information in the synchronization signal block, and first, the BS side traverses all the analog precoding vectors F_RFAnd periodically transmitting a synchronization signal block; the UE side also traverses all the simulation predecoding vectors W of the UE side_RFThe beam information is received so as to traverse all beam pairs between the BS and the UE.

As an alternative embodiment, the combining and constructing the initial arrival and departure angle set from the beam pairs whose received signal strengths are greater than the first threshold value and determining the measurement matrix on each subcarrier includes:

according to the intensity of the received signal, the intensity of the received signal is larger than a first threshold valueAll beam pairs of (a) are ordered, an initial arrival and departure angle set is constructed, and the top N is obtained_RFSimulating a pre-coding vector and a simulating pre-decoding vector corresponding to the group wave beam;

As shown in fig. 3, the present invention can calculate RSRP corresponding to each group of beam pairs to describe the energy of the synchronization signal block under the beam pair communication. Wherein RSRP may be defined as follows:

wherein,

predecoding vector W for receiver simulation_RFThe conjugate transpose of (c). After the initial access is completed, all beam pairs are sorted based on RSRP, and a number P of beam combinations is selected as an initial AoA/AoD set for channel estimation (the number P may be selected according to a preset first threshold).

Meanwhile, the front N is selected according to the RSRP value at the transmitting and receiving end_RFIndividual beam vector construction F_RF/W_RFAnd the vector is used as an analog pre-coding vector and an analog pre-decoding vector of subsequent communication.

In the communication process, after receiving the receiving signal y sent by the BS and extracting the pilot position signal, the UE enters the relevant flow of the channel estimation technology.

As shown in fig. 3, on the premise that the number of channel paths is known, the channel estimation process is set to include two main parts, namely an outer-layer loop and an inner-layer loop, wherein the inner-layer loop realizes AoA/AoD estimation on a certain path through iteration, and the outer-layer loop is used for judging whether to obtain information of all paths.

Before that, in order to recover the millimeterFirstly, according to the initial AoA/AoD set and F acquired in the step 1, the sparse signal of the wave channel in the angle domain_RF/W_RFAnd the pilot sequence constructs a measurement matrix phi for each subcarrier.

Since the initial AoA/AoD set here is a subset of the angular space, it cannot be calculated directly using equation (13).

Suppose AoD and AoA are respectively

That is, AoD is the quantization precision N_tIs the ith quantization angle in the angle space, AoA is the quantization precision N_rRespectively corresponding to A_TAnd A_RColumn i, j in (1), i.e.:

wherein,

and

the ith angle vector in the AOD quantization space and the jth angle vector in the AOA quantization space are represented, respectively.

Further, the air conditioner is provided with a fan,

(i-1) N corresponding to the measurement matrix phi_r+ j column, which may be represented as:

wherein,

and

respectively representing a dimension of N_RFX1 and N_sampleA column vector of x1, and satisfies that the vector elements are all 1.

For A (m,: representing the m-th row of the matrix A, namely a row vector of 1 x n; for a (: n) the nth column of matrix a is denoted, i.e. the column vector representing m x 1.

Similarly, based on the result of beam scanning, the initial AoA/AoD sets are all calculated according to the above equations (15) - (17), so as to obtain the final measurement matrix Φ (the measurement matrix before the inner loop and the measurement matrix before the outer loop are referred to as the initial measurement matrix in this application).

Referring to fig. 3, based on the above steps 1 and 2, the present invention predicts the high-dimensional original channel H between the BS and the UE by using the initial measurement matrix Φ based on the adaptive compressed sensing technology, which mainly includes but is not limited to the following steps:

step 5, recalculating the correlation value between the local measurement matrix and the observed value on the corresponding pilot frequency to determine the new arrival and departure angle corresponding to the maximum correlation value;

and step 9: removing the beam pairs corresponding to the target path from all possible beam pair combinations, recombining the beam pair combinations by the remaining beam pairs, and determining the received signal strength of the pilot signal in each group of beam pairs in the beam pair combinations;

step 11: and calculating the complex gain and the original channel corresponding to each target path according to the target arrival and departure angles and the antenna array response set corresponding to each target path so as to construct the high-dimensional original channel.

Wherein, the steps 3 to 8 belong to an internal circulation part. In the inner loop process, in each iteration, the measurement matrix Φ on each subcarrier is calculated_kAnd corresponding pilot observation y_kThe correlation values of (since the channel estimates are all calculated on the pilots, the index p of the pilots is omitted later), that is, the correlation values of the sensing matrix and the observed values on all the subcarriers are calculated and summed in sequence, which is expressed as follows:

wherein, CorMaxIndex represents the sequence number of the current maximum calculation correlation value; beta is a_lThe sum of the correlation values of the measurement matrix on all the subcarriers and the observed value in the column is obtained; n is the number of subcarriers; index indicates a correlation value.

The invention through beta_lJudging whether the convergence condition is reached in the inner loop in each iteration, calculating the index of the AoD/AoA corresponding to the column according to the CorMaxIndex, and respectively recording the index as m and n, wherein the index comprises the following steps:

further, in step 4, with the arrival and departure angles as the centers, quantizing the surrounding local angle space to obtain a local measurement matrix corresponding to the surrounding local angle space, specifically including:

iteratively updating the arrival and departure angles in the surrounding local angle space by taking the arrival and departure angles as centers, acquiring each updated arrival and departure angle until iteration converges, and outputting local arrival and departure angles; reconstructing a local measurement matrix for each subcarrier of the channel in the frequency domain based on the local arrival and departure angles.

Specifically, higher-precision quantization can be performed in the surrounding local angular space with the AoA/AoD angle corresponding to m, n as the center. Defining the precision R, updating the local AoA/AoD according to the above equation (20) at each iteration:

wherein iter represents the current iteration serial number in the inner loop process, and when the iteration times are larger, the angle interval is smaller, the angle precision is larger, and thus the convergence target angle is tracked.

Further, in each iteration, the local arrival and departure angle φ may be determined based on_local,θ_localAnd the above equation (15) -equation (17) recalculates the local measurement matrix Φ on all subcarriers₁。

Further, Φ can be recalculated₁And the observed value y_pAnd extracting the AoA/AoD index corresponding to the column in which the maximum correlation value is located, which is denoted as m 'and n', and the offset value corresponding to the angle at this time is

Further, the AoA/AoD in the initial angle set are added with the angle offset, and the measurement matrix is updated again according to the above equation (15) -equation (17), and the updated measurement matrix is used as the initial measurement matrix of the next iteration.

Iteratively executing the steps 3-7, and calculating the beta calculated in the current iteration and the previous iteration in each iteration process_lThe absolute value of the difference, and the relation with a preset second threshold is judged:

|β_l-new-β_l-old|＜threshold (21)

if beta is_lIf the absolute value of the difference is smaller than the second threshold, the inner loop iteration termination condition is considered to be satisfied, and the inner loop can be exited.

After the inner loop is finished, the target AoA/AoD of the target path at the end of the iteration and the corresponding measurement matrix can be obtained.

And removing the projection value of the current path in y from the observed value y, and entering outer loop iteration to obtain the target AoA/AoD corresponding to the next path and the corresponding measurement matrix. The expression for removing the projection value of the current path in y from the observed value y may be:

wherein phi is_mA column vector of the measurement matrix phi in the first CorMaxIndex column represents a measurement atom corresponding to the channel path estimated in the current cycle; i is an identity matrix;

is phi_mThe conjugate transpose of (c).

In each iteration process of the outer loop, Yao re-executes the whole flow of the inner loop to determine the estimated target AoA/AoD of each path in each iteration process of the outer loop so as to estimate the complex gains corresponding to different paths, the outer loop can be exited until the estimation information of all the paths is obtained, and the corresponding complex gain alpha is obtained by utilizing the AoA/AoD of each path estimated before_lAnd a high-dimensional original channel H, and finishing the self-adaptive compressed sensing operation; otherwise, repeating the step 2 to the step 9.

In summary, the channel estimation method provided by the present invention designs a massive MIMO channel estimation scheme based on beam scanning and compressive sensing for massive MIMO communication systems such as 5G/B5G, and the specific implementation thereof includes:

BS-side configuration N_tThe root transmitting antenna communicates with a single user, and the UE is equipped with N_rAnd the receiving antenna, wherein the BS end and the UE end both adopt analog beam forming structures, and the antenna array structure is the ULA. The communication channel between the BS end and the UE end adopts a broadband geometric millimeter wave channel and a non-line-of-sight path, and the AOA/AOD of the channel is [0,2 pi ]]The inner parts are uniformly distributed.

The channel estimation provided by the invention is repeated, preferably based on the beam scanning stage of the BS and the UE in the initial access process, the BS and the UE traverse all communication beam pairs through a synchronous signal block, measure the RSRP of all the beam pairs and sort the RSRP from large to small.

Because each group of beam pairs at the transceiving end corresponds to respective AoA/AoD, the beam pairs with the RSRP larger than the first threshold value can be provided for a channel estimation algorithm through beam scanning to form an alternative beam space, and further a measurement matrix phi is constructed.

On the basis of beam scanning, the method converts the original high-dimensional channel estimation problem into sparse channel estimation of an angle domain, and recovers channel information by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode.

Fig. 4 is a schematic structural diagram of a Synchronization Signal Block in a 5GNR in a time-frequency domain, and taking a beam management mechanism in a 5G NR as an example, as shown in fig. 4, a BS and a UE use a Synchronization Signal Block (SSB) to carry beam information of a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS) and a Physical Broadcast Channel (PBCH) to complete a beam scanning process, and the user obtains all traversed beam information and corresponding RSRP and provides an initial AoA/AoD set and a measurement matrix Φ with a larger RSRP.

The channel estimation method needs to be implemented based on the observed value of the transmission pilot, the original pilot sequence and the measurement matrix Φ. In order to recover the sparse channel of the angle domain, the whole algorithm flow is divided into an outer circulation part and an inner circulation part.

And on the premise that the number of the paths in the channel is known, sequentially calculating the information of each path in the channel by iteration in the inner loop, wherein the information comprises AoA/AoD and path gain. The inner loop continuously tracks the angle to be estimated based on multiple iterations to reduce the angle range and improve the quantization precision, namely, firstly, the measurement matrix phi on all subcarriers and the corresponding observed values are taken to carry out the correlation value operation of the formula (18); and then, carrying out higher-precision quantization around the local angle to obtain an angle deviation value, updating the measurement matrix and the quantized AoA/AoD angle, and exiting the inner loop after convergence is achieved after multiple iterations to obtain the estimation information of the current path.

After the information of a certain path is estimated, the outer loop removes the influence of the path on signal transmission from the observed value, specifically as shown in the above formula (22), and after all paths are estimated, the complex gain of each path is calculated by using all the estimated AoA/AoD information, thereby recovering the original high-dimensional channel.

Fig. 5 is a simulation result diagram of channel estimation Normalized Mean Square Error (NMSE) under different algorithm comparisons, fig. 6 is a simulation result diagram of block error rate (Bler) under different algorithm comparisons, simulation parameters satisfy the following table 1, and the antenna configuration is 256 × 16, and the initial beam pair number P of the adaptive omp BM algorithm is 200.

TABLE 1 common simulation parameter configuration

The channel estimation method provided by the invention is marked as AdaptveOMP BM, and the comparison algorithms are Ideal angle, AdaptveOMP NonBM and OMP respectively. Wherein Ideal angle is an Ideal AoA/AoD angle, which is equivalent to the upper performance bound. The AdaptiveOMP nobm algorithm performs channel estimation without using beam scanning, i.e. by matching the complete AoA/AoD quantization angle space with steps 3-11 in fig. 3. OMP is a traditional orthogonal matching tracking algorithm, the influence of AoA/AoD random angles is not considered, and only an estimation angle can be selected from a quantization angle space.

From the simulation results shown in fig. 5 and fig. 6, the adaptive omp BM achieves better channel estimation performance and has a small difference from the performance upper bound provided by the Ideal angle algorithm. The OMP algorithm only obtains the quantized angle, and thus the channel estimation performance is poor.

The performance of the AdaptveOMP NonBM algorithm is similar to that of the AdaptveOMP BM algorithm provided by the invention, but the algorithm complexity is higher due to a larger-scale initial angle set. Specifically, the number of subcarriers is K, and the number of complete angle combinations is N_tN_r，N_pathN_iterThe total number of internal and external cycles in the algorithm of fig. 3, with the constant C.

By analysis, the calculation complexity corresponding to the AdaptiOMP NonBM algorithm is O ((2 KxN)_rN_t+C)×N_pathN_iter) In the adaptive omp BM algorithm provided in the present invention, according to the 5G NR protocol, the base station needs to periodically send a beam to scan the corresponding synchronization signal block, so that it is not necessary to introduce extra computational overhead for the channel estimation algorithm, and therefore, the computational complexity of the adaptive omp BM algorithm is O ((2K × P + C) × N)_pathN_iter) The calculation times are reduced by O (2 Kx) (N) compared with the AdaptiOMP NonBM algorithm_rN_t-P)×N_pathN_iter)。

Fig. 7 is a simulation result diagram of the normalized mean square error of the channel estimation of the algorithm provided by the present invention under different antenna configurations, and fig. 8 is a simulation result diagram of the block error rate of the algorithm provided by the present invention under different antenna configurations, where different antenna configurations are 128 × 8, 128 × 16, 256 × 16, and the like, and the common simulation parameters are shown in table 1.

In combination with the simulation results of fig. 7 and fig. 8, the larger the number of antennas is, the higher the division accuracy of the initial quantization angle is, and a larger beam gain is formed, thereby improving the channel estimation performance.

Fig. 9 is a simulation result diagram of the normalized mean square error of the channel estimation of the algorithm provided by the present invention under the condition that the beam scanning provides different initial AoA/AoD quantities, and fig. 10 is a simulation result diagram of the block error rate of the algorithm provided by the present invention under the condition that the beam scanning provides different initial AoA/AoD quantities, wherein the number of the beam pairs is set to be P10, 20,200, and the common simulation parameters are shown in table 1.

From the simulation results of fig. 9 and 10, although the channel estimation and signal transmission performance are sequentially improved as the number P of initial beam pairs increases, the algorithm complexity formula O ((2K × P + C) × N)_pathN_iter) In view of the above, the calculation delay is greatly increased, so that a compromise between the transmission performance and the algorithm complexity can be found, and better transmission performance can be realized with lower algorithm complexity.

In summary, the channel estimation method provided by the present invention, based on the 5G/B5G massive MIMO communication system, provides a massive MIMO channel estimation method based on beam pair scanning and compressive sensing techniques, in the initial phase of beam pair scanning, the base station and the user terminal traverse all communication beam pairs through a synchronization signal block, measure the signal strengths of all beam pairs and sequence the beam pairs from large to small to construct a measurement matrix; on the basis, the high-dimensional original channel estimation problem is converted into sparse channel estimation of an angle domain, channel information is recovered by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode, and accurate estimation of a channel can be realized with low algorithm complexity.

Fig. 11 is a schematic structural diagram of a channel estimation apparatus provided in the present invention, and as shown in fig. 11, the channel estimation apparatus mainly includes a signal acquisition unit 111 and a signal analysis unit 112

The signal acquisition unit 111 is mainly used for constructing a measurement matrix according to the beam pair scanning result;

the signal analysis unit 112 is mainly configured to predict a high-dimensional original channel between the base station and the user terminal by using the measurement matrix based on an adaptive compressed sensing technique.

It should be noted that, when the channel estimation apparatus provided in the embodiment of the present invention is in specific operation, the channel estimation method described in any of the above embodiments may be executed, and details of this embodiment are not described herein.

The invention provides a channel estimation device, which is applied to a large-scale MIMO communication system of 5G/B5G and provides a large-scale MIMO channel estimation method based on beam pair scanning and compressed sensing technology.A base station and a user terminal traverse all communication beam pairs through a synchronous signal block at the initial stage of beam pair scanning, measure the signal intensity of all the beam pairs and sequence the beam pairs from large to small to construct a measurement matrix; on the basis, the high-dimensional original channel estimation problem is converted into sparse channel estimation of an angle domain, channel information is recovered by using a compressed sensing technology and adopting a local angle quantization and self-adaptive angle tracking mode, and accurate estimation of a channel can be realized with low algorithm complexity.

Fig. 12 is a schematic structural diagram of an electronic device provided in the present invention, and as shown in fig. 12, the electronic device may include: a processor (processor)1210, a communication Interface (Communications Interface)1220, a memory (memory)1230, and a communication bus 1240, wherein the processor 1210, the communication Interface 1220, and the memory 1230 communicate with each other via the communication bus 1240. Processor 1210 may invoke logic instructions in memory 1230 to perform a method of channel estimation comprising: constructing a measurement matrix according to the beam pair scanning result; and predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on an adaptive compressed sensing technology.

In addition, the logic instructions in the memory 1230 may be implemented in software functional units and stored in a computer readable storage medium when the logic instructions are sold or used as a stand-alone product. Based on such understanding, the technical solution of the present invention or a part thereof which substantially contributes to the prior art may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

In another aspect, the present invention also provides a computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions which, when executed by a computer, enable the computer to perform a channel estimation method provided by the above methods, the method comprising: constructing a measurement matrix according to the beam pair scanning result; and predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology.

In yet another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored, the computer program being implemented by a processor to perform the channel estimation method provided in the above embodiments, the method including: constructing a measurement matrix according to the beam pair scanning result; and predicting a high-dimensional original channel between the base station and the user terminal by utilizing the measurement matrix based on the self-adaptive compressed sensing technology.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A method of channel estimation, comprising:

constructing a measurement matrix according to the beam pair scanning result;

2. The channel estimation method of claim 1, wherein the constructing the measurement matrix according to the beam pair scanning result comprises:

3. The channel estimation method according to claim 2, wherein the predicting a high-dimensional original channel between the base station and the user terminal based on the adaptive compressed sensing technology by using the measurement matrix comprises:

step 3, calculating a correlation value between the initial measurement matrix and the observed value on the corresponding pilot frequency to obtain an arrival and departure angle corresponding to the maximum correlation value;

4. The channel estimation method according to claim 2, wherein the traversing all possible beam pair combinations for the base station to communicate with the user terminal through beam pair scanning and determining the received signal strength of the pilot signal in each group of beam pair directions in the beam pair combinations comprises:

5. The channel estimation method of claim 4, wherein the combining the beam pairs with the received signal strength greater than the first threshold to construct an initial arrival and departure angle set and determine the measurement matrix on each subcarrier comprises:

according to the intensity of the received signal, sequencing all the wave beam pairs with the received signal intensity larger than a first threshold value, constructing an initial arrival and departure angle set, and acquiring the top N_RFSimulating a pre-coding vector and a simulating pre-decoding vector corresponding to the group wave beam;

6. The channel estimation method of claim 3, wherein the calculating the correlation value between the initial measurement matrix and the observed value on the corresponding pilot to obtain the arrival and departure angle corresponding to the maximum correlation value comprises:

and sequentially calculating and summing correlation values of the initial measurement matrix on each subcarrier and the observation value on the corresponding pilot frequency to obtain a correlation value between each column of the initial measurement matrix and the observation value on the corresponding pilot frequency, and determining a column corresponding to the maximum correlation value from the correlation values to obtain the arrival and departure angles corresponding to the maximum correlation value.

7. The channel estimation method of claim 3, wherein the quantizing the surrounding local angle space with the arrival and departure angle as a center to obtain a local measurement matrix corresponding to the surrounding local angle space comprises:

8. A signal channel estimation device, comprising:

9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the channel estimation method steps according to any of claims 1 to 7 when executing the computer program.

10. A non-transitory computer readable storage medium, having stored thereon a computer program, when being executed by a processor, for performing the channel estimation method steps according to any of claims 1 to 7.